homeostasis

Question 1

explain the effect of sweating on the body

Answer 1

1 evaporation will , have a cooling effect /
reduce (body) temperature ;
2 heat , taken from / supplied by ,
the body / blood / skin , is ,
needed / used for , evaporation ;
3 idea that water has a high latent heat of ,
vaporisation / evaporation ;

Question 2

suggest why shivering occurs during a fever

Answer 2

) idea that to increase body temperature as it is
lower than the ‘new’ set-point
(even though body is hot) ;

Question 3

why is vasodilation at times dangerous

Answer 3

1 vasodilation results in more blood nearer to the
skin surface ;
2 idea that will lose (even) more heat /
further heat loss (from body) /
body temperature decreases further ;
3 (named) organ(s) will not be able to maintain ,
function / metabolism ;

Question 4

State where the core body temperature is monitored.

Answer 4

(thermoregulatory centre in) hypothalamus

Question 5

Name the type of sensory cell in the skin that detects changes in environmental temperature.

Answer 5

thermoreceptor / peripheral temperature receptor ;

Question 6

Name the corrective homeostatic mechanism that works to restore any changes in body temperature to the normal range.

Answer 6

negative feedback / thermoregulation

Question 7

Elephants have large, thin ears that they move backwards and forwards when hot.

Answer 7

large surface area (to lose heat) ;
(thin) so , blood flows / (named) blood vessel are ,
close to the (skin) surface (to lose heat) ;
(movement) increases air movement over , skin / surface
(to lose heat) ;

Question 8

Penguins living in cold climates have ‘shunt’ blood vessels. These shunt vessels link arterioles carrying blood towards their feet with small veins that carry blood away from their feet.

Answer 8

blood loses less heat because ,
less blood flows to feet /
warm blood diverted from arterioles to veins
or
less blood flows to feet so core body temperature
maintained ;

Question 9

Explain what is meant by the terms autotroph and heterotroph.

Answer 9

autotroph
can make ,
organic molecule(s) / named organic molecule(s) ,
from , inorganic molecule(s) / carbon dioxide ;
heterotroph
relies on / needs to use / has to obtain /
feeds on and digests ,
(named) organic molecules (that have been made
by another organism) ;

Question 10

State precisely where the cells that detect a decrease in the water potential of the blood plasma are found.

Answer 10

((walls of) blood vessels in) hypothalamus ;

Question 11

Name the cells that detect this decrease.

Answer 11

osmoreceptor(s) ;

Question 12

animals that are able to regulate and maintain their core body temperature within narrow limits;

Answer 12

endotherm(s) ;

Question 13

the increase in the diameter of the lumen of an arteriole to allow more blood to flow through.

Answer 13

(vaso)dilation ;

Question 14

Name a hormone that increases the metabolic rate and so generates heat.

Answer 14

thyroxine / adrenaline;

Question 15

Name the part of the brain where the thermoregulatory centre is located.

Answer 15

hypothalamus ;

Question 16

Explain what is meant by the term homeostasis.

Answer 16

1 idea of maintaining (relatively) stable internal ,
 environment / state ;
2 within (narrow) limits / within (narrow) range /
 about a set point ;
3 even though environment is changing ;

Question 17

Explain the likely effect on the blood cells if the water potential of the plasma was allowed to increase significantly.

Answer 17

water potential /  , of plasma / outside cells ,
would be higher than that of the (blood) cells ;
water would enter (blood) cells ;
blood cells , swell / (might) burst / lyse ;

Question 18

Describe the way in which an endothermic animal, such as a mammal, normally prevents its body temperature from decreasing when the external temperature decreases.

Answer 18

peripheral / skin , thermoreceptors / (heat) receptors ,
stimulated (by decrease in external temp) ;
(impulses sent to / blood temperature monitored in )
hypothalamus / sensory cortex ;
vasoconstriction of , arterioles / small arteries , to reduce heat loss ;
(prevents heat loss by) radiation / conduction / convection ;
increased , metabolic rate / metabolism / respiration ,
to generate heat (energy) ;
(release of) adrenaline / thyroxine ;
shivering / (involuntary) muscle spasms , to generate heat (energy) ;
erector / hair , muscles raise , (skin) hair / fur , to trap , air / heat ;
QWC
peripheral, thermoreceptor(s),
hypothalamus, cortex,
vasoconstriction, metabolic rate / metabolism,
adrenaline, thyroxine,
erector radiation / conduction / convection